#2975-Suggestion-Add-Permissions-Policy-as-configurable-option-to-SecureHeaders-GatewayFilter

- added Permissions-Policy header as an opt-in header & default value
- updated documentation with Permissions-Policy and resources
- updated tests to include Permissions-Policy
- SecurityHeaders and Permissions-Policy may be configured globally / per route
- updated structure of public methods and class members to match previous version structure

Fixes gh-2975

Signed-off-by: Jörg Richter <96986086+joerg-richter-5234@users.noreply.github.com>

spring-cloud-gateway-sample/src/main/resources/application-secureheaders.yml

@@ -0,0 +1,50 @@
+test:
+    hostport: httpbin.org:80
+  #  hostport: localhost:5000
+    uri: http://${test.hostport}
+  #uri: lb://httpbin
+
+
+spring:
+  cloud:
+    gateway:
+      filter:
+      default-filters:
+      #- PrefixPath=/httpbin
+      #- AddResponseHeader=X-Response-Default-Foo, Default-Bar
+
+      routes:
+      # =====================================
+      # to run server
+      # $ wscat --listen 9000
+      # to run client
+      # $ wscat --connect ws://localhost:8080/echo
+      - id: websocket_test
+        uri: ws://localhost:9000
+        order: 9000
+        predicates:
+        - Path=/echo
+      # =====================================
+      - id: default_path_to_httpbin_secureheaders
+        uri: ${test.uri}
+        order: 10000
+        predicates:
+        - Path=/**
+        filters:
+          - name: SecureHeaders
+            args:
+              disable: x-frame-options
+              enable: permissions-policy
+              permissions-policy : geolocation=("https://example.net")
+
+logging:
+  level:
+    org.springframework.cloud.gateway: TRACE
+    org.springframework.http.server.reactive: DEBUG
+    org.springframework.web.reactive: DEBUG
+    reactor.ipc.netty: DEBUG
+    reactor.netty: DEBUG
+
+management.endpoints.web.exposure.include: '*'
+
+